This is considered a RARE lens and not much info has been found online about it.

-It has 6 blades.
-On the filter thread can be read "U Mount" which means it's an M42 mount lens.
-It takes 49mm filters.
-This is a very compact (but not quiet a pancake) lens.
Its aperture is in the range of f/2.1 to f/16.

This is a hard to find lens.
It's lightweight, compact, has a bubbly bokeh, wide open is a bit soft. Call it "glamour" look... ok, maybe not too sharp wide open, specially when shooting further that 3 feet from subject.
Contrast and color rendering: 7/10
Some chromatic aberration present wide open and very improved at f/4
On test, shooting at 30 degrees of light source starts showing some ghost/flare, which I suspect comes from non-coated front element.
Focus throw is about 80/85 degrees.
Definitely a "close portrait" kind of lens.

Only negative observation is that the closest it can focus is almost 2 feet.

Photo below was taken wide open (f/2.1) at the closest focusing distance.